1. Field of the Invention
The present invention relates to a contact with dual compliant pin sections used in an electrical connector, especially a contact having dual compliant pin sections used in a zero insertion force socket on which a CPU module is mounted.
2. The Prior Art
An electrical connector especially a zero insertion force (ZIF) socket has been used to connect a CPU to a printed circuit board for years. Normally, this socket needs a relatively long pitch for adopting a lead-in distance of each contact which allows a corresponding CPU pin to be inserted into the socket with substantially zero insertion force firstly and then moved by a cover of the socket for this lead-in distance to abut against contacting portion of the contact in the socket. These sockets may be referred to U.S. Pat. Nos. 5,057,031 and 5,730,615. However, the contacts of the above patents if directly used in a ball grid array soldering process will cause some problems during the soldering process or during later operation. One of the serious problems is the damage to the soldering ball due to frequent on-off of the CPU which causes fatigue of the solder ball because of long term of temperature variation due to frequent on/off of the CPU.
Another serious problem is that coefficients of thermal expansion between the socket and the printed circuit board are different during soldering (at a very high temperature) thereby resulting in tension in the solder ball. This tension if not released will damage the solder ball thus negatively affecting the normal conducting between the socket and the printed circuit board.
For solving these problems, it is requisite to provide a new contact which has a compliant pin section to efficiently absorb the unwanted tension occurred or stored in the solder ball.
Although the inventor of this application has applied a U.S. patent application Ser. No. 09/146,998 relating to a low profile socket and the contacts thereof, he does not particularly point out this problem in that application and no claims related to the compliant pin section of the contact. Moreover, the contact as disclosed in U.S. patent application Ser. No. 09/146,998 does not have an additional compliant pin section which can guarantee the CPU pin be stably and properly engaged between two contacting sections of the contact thereof. For example, sometimes the CPU pin may be in contact with one of the contacting portions tightly while in contact with the other contacting portion loosely, thus causing unstable contacting and resulting in unstable impedance. Therefore, this application is focused on the dual compliant pin sections of the contact which is distinguished from the U.S. patent application Ser. No. 09/146,998.